1. Field of the Invention
The present invention relates to a semiconductor device and method of a manufacturing the same.
This application is counterpart of Japanese patent applications, Serial Number 194873/2003, filed Jul. 10, 2003, the subject matter of which is incorporated herein by reference.
2. Description of the Related Art
A dicing method using a rotating blade has heretofore been used upon individualizing a wafer such as a silicon substrate in which semiconductor elements or the like are formed and built in a wafer process, into a plurality of pieces of chips.
The dicing method using the blade is used even in a case in which a wafer subsequent to an external terminal forming process is individualized in a WCSP (Waferlevel Chip Size Package) manufacturing process.
In recent years, attention has been given to a device provided with an SOS (Silicon On Sapphire) substrate in which a silicon thin film is formed on a sapphire layer, in terms of low power consumption and speeding up.
However, the sapphire constituting the SOS substrate is high in hardness next to the diamond. Therefore, when dicing is effected on the sapphire substrate, it is performed in a state in which the rotational speed of a blade is held extremely low (at a rotational speed equivalent to a few one-tenth to one-hundredth the normal rotational speed) or a dicing method using laser light is used.
A method using thermal fusion by laser light has heretofore been utilized as the dicing method using the laser light. However, it has many problems to be solved, such as thermal distortion, contamination, etc.
To this end, a non-heated processing system (or also called non-fusion system) has recently been proposed as a new laser light-based dicing method. Described specifically, there are known a stealth dicing method (see the following Patent Document 1, for example) developed by Hamamatsu Photonics KK, and a shortpulse laser developed by Disco Co., Ltd.
(Patent Document 1)
Japanese Laid Open Patent Application No. 2002-192370
However, when the above-mentioned dicing method using the blade is utilized, there is a need to set a margin ranging from several tens of μm to several hundreds of μm rather than a chip size. This is because a kerf width produced upon dicing, pitching developed by impact of dicing, etc. must be taken into consideration.
Therefore, a chip size larger than an actual chip size must be designed. Thus, since the collected number of chips per wafer decreases, the cost of each product increases.
When the SOS substrate is used in particular, a long period of time is required for dicing because the sapphire substrate is a grinding resistant material, and this is another issue to consider in addition to kerf width and dicing. As a result, the blade is wasted earlier, thus causing a substantial increase in cost.
Similarly even in the case of WCSP, a package size must be designed larger than an actual package size, thus increasing the product cost.
On the other hand, when the above non-heated processing system (or also called non-fusion system) is utilized, the kerf width and pitching are almost undeveloped and high-speed dicing is made possible as compared with the dicing method using the blade.
However, the non-heated processing type dicing involves the following problems.
A permeability resistant portion hard to cause laser light to pass therethrough might be interposed in a laser optical path upon application of the laser light to a target to be processed.
At this time, the rate of convergence of the laser light into the target is reduced due to the fact that the execution of dicing becomes impossible or the laser light is scattered over the surface of the target. As a result, a remarkable kerf width and pitching might be developed.
As such a permeability resistant portion, may be mentioned, for example, a metal film for a process monitoring TEG, a seal layer at a WCSP, etc. all provided on a dicing line of a wafer.
With an increase in demand for high integration of a recent semiconductor device, the practical application of a thinned silicon substrate or the like is urgently necessary. Since, however, the kerf width and pitching become noticeable with substrate's thinning, many technical problems arise under existing circumstances.
Therefore, an object of the present invention is to provide a semiconductor device which makes it possible to apply non-fusion type dicing using laser light regardless of a structural form of a target to be processed, thereby to suppress the occurrence of a kerf width and pitching, and a manufacturing method thereof.